It has been conventional to apply a relatively resilient air-impervious coating of polymeric/copolymeric material to the interior of tires by a spraying process, particularly prior to the retreading thereof. During the retreading process, the polymeric/copolymeric coating prevented pressurized air from migrating from the interior of the tire to the interface between the buffed outer surface and the new tread thereby assuring an excellent bond between the "old" tire and the "new" rubber/pre-cure bonded thereto. Such retreads, when in use, also tended not to develop "leakers" as readily as uncoated tires since the polymeric/copolymeric coating material prevented air under pressure from escaping through the tire/carcass, particularly if the latter was relatively old, porous, worn, cracked or the like. While it might be expected that tires so coated would not leak or leak appreciably less than uncoated tires, it was noted that in actual practice tires so coated at least appeared to deflate at a percentage greater than that which was expected. This was particularly true in large tractor-trailer tires but was found to be just as equally true in smaller garden-type riding tractors, as well as passenger automobile tires.
While the industry has seemingly directed its efforts toward reducing/eliminating air migration through the tires, be they new, after-market or retread, applicants herein began their investigation of leakage with the assumption that air migration through the tires per se was virtually eliminated by standard practices/coatings, and there must be some underlying cause for deflation/leakage. Through observation, analysis and experimentation, it was found that apart from leakage through new and recap tires, leakage also occurred (1) between conventional rims and associated valves, (2) between tire beads and wheel rim beads, and, most surprisingly, (3) through interstices in the metallic rims and porous welds associated therewith, particularly in the case of small garden-type rims formed of two welded bodies. Some leakage also occurred (4) simply because of dirt and rust between the metallic wheel beads and the tire beads, particularly in the case of after market recap/retread tires which are simply reapplied to dirty/rusted wheel rims essentially incapable of maintaining an air-impervious seal therebetween.
Accordingly, the invention provides a novel method of preventing air leakage from associated inflated tires mounted on metallic rims by (a) first cleaning and derusting the associated rims and (b) thereafter entirely coating all surfaces of the rim with an air impervious coating of resilient polymeric material whereby the porosity/nicks/cracks/remaining dirt/rust, etc. is coated and effectively sealed against air migration in association with a new or retread tire bead and an associated air valve body.